In recent years, as a measure toward low-energy consumption and global warming prevention, research in the field of lighting has led to an illumination device that uses LEDs (Light-Emitting Diodes) to realize greater energy efficacy than conventional incandescent light bulb technology.
For example, the energy efficacy of existing incandescent light bulbs, on the order of some tens of lumens per watt, can be realized at levels of 100 lm/W and above by using LEDs for the light source (a bulb-shaped illumination device using LEDs and intended as a replacement bulb being hereinafter referred to as an LED light bulb).
Patent Literature 1 proposes an LED light bulb as a replacement for a conventional incandescent light bulb. The LED light bulb described in Patent Literature 1 has a light-emitting module made up of a substrate on which are mounted a plurality of LEDs, the module being fitted onto an end (a surface) of a case comprising a lighting circuit therein, and a dome-shaped globe that covers the LEDs. The outward appearance of this LED light bulb is similar to that of conventional incandescent light bulbs. The LED light bulb uses an Edison screw base as a power supply terminal, and can thus be fixed into a light fixture made for use with conventional incandescent light bulbs.
In the above-described LED light bulb, the light-emitting module is fixed onto the surface of the case by screwing through the middle with penetrating screws.
Nevertheless, the heat generated by the light-emitting module during luminescence must be transmitted through the case (acting as a heat sink) or similar. There is thus a need for the case or the like to be in contact with the bottom surface of the light-emitting module.
As such, technology has been developed in which the light-emitting module is fixed onto a mount member of the case or heat sink such that the bottom surface of the light-emitting module is in contact with the mount member. There, a socket for the light-emitting module is fastened onto the mount member (heat sink) with the exception of the portion of the light-emitting module on which the LEDs are mounted (portion hereinafter termed light-emitting unit) (see Patent Literature 2 and 3). The socket has a plurality of compression springs that, upon receiving the light-emitting module placed on the mount member (heat sink), presses the top side of the area surrounding the light-emitting unit of the light-emitting module toward the mount member (heat sink). Being pressed toward the mount member by the compression springs, the bottom surface of the light-emitting module is brought into contact with the mount member. The compression springs are capable of regulating the movement (sliding) of the light-emitting module on the mount member.